Closed-loop shaping based on Nevanlinna-Pick interpolation with a degree bound

This note presents a novel method for shaping the frequency response of a single-input-single-output closed-loop system, based on the theory of Nevanlinna-Pick interpolation with degree constraint. The method imposes a degree bound on the closed-loop transfer function and searches for a function with a desired frequency response. Numerical examples illustrate the potential of the method in designing controllers with lower degrees than the ones obtained by conventional H/sup (infinity)/ controller design methods with weighting functions.